<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>js与html三种结合方式</title>
    <script>
        window.alert("Hello World111");
    </script>
    <script type="text/javascript" src="demo1.js"></script>
</head>
<body>
<script>
    window.alert("Hello World333");
</script>
<label>
    <input id="username" name="username" type="text" value="admin">
    <button name="button" onclick="window.alert('Hello World444')">点击我</button>
</label>
<script>
    let ele = document.getElementById("username");
    let value = ele.value;
    alert(value);
</script>


</body>
</html>